<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>v-if指令</title>
  </head>
  <body>
    <!--  v-if：根据表达式的真假切换元素的显示状态 -->
    <!-- 和v-show区别：v-if是直接隐藏dom，v-show是样式隐藏 -->
    <div id="app">
      <input type="button" value="切换显示状态" @click="toggleIsShow" />
      <p v-if="isShow">我出来啦</p>
      <p v-show="isShow">我出来啦 v-show</p>
      <p v-if="tm>=30" @click="clickTm">太热了</p>
    </div>

    <!-- 开发环境版本，包含了有帮助的命令行警告 -->
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    <script>
      var app = new Vue({
        el: "#app",
        data: {
          isShow: false,
          tm:40
        },
        methods: {
          toggleIsShow: function () {
            this.isShow = !this.isShow;
          },
          clickTm:function(){
              this.tm--,
              console.log(this.tm)
          }
        },
      });
    </script>
  </body>
</html>
